1. Field of the Invention
The present invention relates to a quartz crystal tuning fork resonator, capable of operating in a flexural mode.
2. Background Information
Quartz crystal tuning fork resonators, which are capable of vibrating in a flexural mode, are widely used as a time standard in consumer products, wearable time-keeping equipment and communication equipment (such as wristwatches, cellular phones, and pagers). Recently, because of miniaturization and the light weight nature of these products, the need for a smaller quartz crystal tuning fork resonator capable of operating in a flexural mode and having a small series resistance and a high quality factor has arisen.
Heretofore, however, it has been impossible to obtain a conventional miniaturized, quartz crystal tuning fork resonator, capable of operating in a flexural mode, and having a small series resistance and a high quality factor. When miniaturized, the conventional quartz crystal tuning fork resonator capable of operating in a flexural mode, as shown in FIG. 22 (which has electrodes on the obverse faces 203, 207, reverse faces 204, 208 and the four sides 205, 206, 209, 210 of each tuning fork tine, and as also shown in FIG. 23, which is a cross-sectional view of the tuning fork tines of FIG. 22), has a smaller electromechanical transformation efficiency, which provides a small electric field (i.e. Ex becomes small), a large series resistance, and a reduced quality factor. In FIG. 22, a conventional tuning fork resonator 200 is shown with tuning fork tines 201, 202 and tuning fork base 211.
In addition, it has heretofore been impossible to obtain a quartz crystal tuning fork resonator, capable of operating in a flexural mode, and having a small frequency change over a wide temperature range of between −10° C. to +50° C., because the resonator typically has a temperature coefficient with a parabolic curve, and a second order temperature coefficient of approximately −3.5×10−8/° C.2. This value is comparatively large as compared with AT cut quartz crystal resonators vibrating in thickness shear mode.
Accordingly, it is, therefore, a general object of the present invention to provide embodiments of a quartz crystal tuning fork resonator, capable of operating in a flexural mode, which overcome or at least mitigate one or more of the above problems.